/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.lucene.analysis;

import java.io.File;
import java.io.IOException;
import java.io.Reader;
import java.util.Set;

import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.ReusableAnalyzerBase;
import org.apache.lucene.analysis.WordlistLoader;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.Version;

/**
 * Base class for Analyzers that need to make use of stopword sets. 
 * 
 */
public abstract class StopwordAnalyzerBase extends ReusableAnalyzerBase {

    /**
     * An immutable stopword set
     */
    protected final CharArraySet stopwords;

    protected final Version matchVersion;

    /**
     * Returns the analyzer's stopword set or an empty set if the analyzer has no
     * stopwords
     * 
     * @return the analyzer's stopword set or an empty set if the analyzer has no
     *         stopwords
     */
    public Set<?> getStopwordSet() {
        return stopwords;
    }

    /**
     * Creates a new instance initialized with the given stopword set
     * 
     * @param version
     *          the Lucene version for cross version compatibility
     * @param stopwords
     *          the analyzer's stopword set
     */
    protected StopwordAnalyzerBase(final Version version, final Set<?> stopwords) {
        matchVersion = version;
        // analyzers should use char array set for stopwords!
        this.stopwords = stopwords == null ? CharArraySet.EMPTY_SET : CharArraySet.unmodifiableSet(CharArraySet.copy(version, stopwords));
    }

    /**
     * Creates a new Analyzer with an empty stopword set
     * 
     * @param version
     *          the Lucene version for cross version compatibility
     */
    protected StopwordAnalyzerBase(final Version version) {
        this(version, null);
    }

    /**
     * Creates a CharArraySet from a file resource associated with a class. (See
     * {@link Class#getResourceAsStream(String)}).
     * 
     * @param ignoreCase
     *          <code>true</code> if the set should ignore the case of the
     *          stopwords, otherwise <code>false</code>
     * @param aClass
     *          a class that is associated with the given stopwordResource
     * @param resource
     *          name of the resource file associated with the given class
     * @param comment
     *          comment string to ignore in the stopword file
     * @return a CharArraySet containing the distinct stopwords from the given
     *         file
     * @throws IOException
     *           if loading the stopwords throws an {@link IOException}
     */
    protected static CharArraySet loadStopwordSet(final boolean ignoreCase, final Class<? extends ReusableAnalyzerBase> aClass, final String resource, final String comment) throws IOException {
        Reader reader = null;
        try {
            reader = IOUtils.getDecodingReader(aClass.getResourceAsStream(resource), IOUtils.CHARSET_UTF_8);
            return WordlistLoader.getWordSet(reader, comment, new CharArraySet(Version.LUCENE_31, 16, ignoreCase));
        } finally {
            IOUtils.close(reader);
        }

    }

    /**
     * Creates a CharArraySet from a file.
     * 
     * @param stopwords
     *          the stopwords file to load
     * 
     * @param matchVersion
     *          the Lucene version for cross version compatibility
     * @return a CharArraySet containing the distinct stopwords from the given
     *         file
     * @throws IOException
     *           if loading the stopwords throws an {@link IOException}
     */
    protected static CharArraySet loadStopwordSet(File stopwords, Version matchVersion) throws IOException {
        Reader reader = null;
        try {
            reader = IOUtils.getDecodingReader(stopwords, IOUtils.CHARSET_UTF_8);
            return WordlistLoader.getWordSet(reader, matchVersion);
        } finally {
            IOUtils.close(reader);
        }
    }

    /**
     * Creates a CharArraySet from a file.
     * 
     * @param stopwords
     *          the stopwords reader to load
     * 
     * @param matchVersion
     *          the Lucene version for cross version compatibility
     * @return a CharArraySet containing the distinct stopwords from the given
     *         reader
     * @throws IOException
     *           if loading the stopwords throws an {@link IOException}
     */
    protected static CharArraySet loadStopwordSet(Reader stopwords, Version matchVersion) throws IOException {
        try {
            return WordlistLoader.getWordSet(stopwords, matchVersion);
        } finally {
            IOUtils.close(stopwords);
        }
    }
}
